1. Field of the Invention
This invention relates to methods of, and apparatus for, securing single ply membranes to roofs. Those membranes are made of thermoplastic or elastomeric material; and they are laid directly on roofs or on substrates on roofs. It is important to secure the single ply membranes in an inexpensive but effective manner.
2. Description of the Prior Art
Single ply membranes are customarily held in place on roofs or on substrates on roofs by (a) placing river gravel or concrete pavers on the top surfaces of those membranes to hold them in position, (b) using adhesive to bond the single ply membranes to substrates on the roofs, or (c) placing batten bars on the single ply membranes at spaced intervals and then passing fasteners downwardly through those bars and those membranes to secure those batten bars and membranes to the roofs.
River gravel is desirable because it is largely free of sharp edges; but river gravel is not always available in quantity at economical prices. Concrete pavers are more expensive than river gravel; and they do not have the desirable rounded surfaces of river gravel. Also, whether river gravel or concrete pavers are used, they constitute an undesirable constant dead weight on a roof, because current practices call for a minimum loading of ten pounds per square foot of roof. Also, river gravel and concrete pavers impede free pedestrian or vehicular movement across roofs. As a result, the use of river gravel or concrete pavers to secure single ply membranes to roofs is objectionable.
Where an adhesive is used to secure single ply membranes to substrates on roofs, the adhesive must be compatible with the material of the membranes and also must be compatible with the material of the substrates on the roofs. A substrate usually takes the form of insulation that is mechanically secured to the roof by fasteners or is adhered to the roof by asphalt. Where insulation is adhered to the roof by asphalt, additional securement of that insulation against lateral shifting is usually required. A critical problem in the use of adhesives to secure single ply membranes to substrates on roofs is the problem of avoiding wrinkles as the membranes are placed in engagement with the adhesive-coated substrates; and a further critical problem is the attainment of a complete bond of the membranes to the substrates. Also, the amount of adhesive, the cost of fasteners or asphalt used to secure the substrates to the roofs, and the time involved in keeping wrinkles from forming in the membranes can make the use of adhesives, to secure single ply membranes to roofs, relatively expensive.
The use of batten bars to secure single ply membranes to roofs avoids the dead weight constituted by river gravel or concrete pavers, provides minimum impedance to pedestrian or vehicular traffic on roofs, avoids the wrinkling that frequently occurs when the membranes are secured to substrates on roofs by adhesives, and is less expensive than river gravel, concrete pavers or adhesives. However, the batten bars which have been used heretofore have been objectionable because they were made from metal, and hence could not be drilled without exposing the walls of the drilled holes therein to corrosive attack. Also, the oils on the upper surfaces of those bars made it difficult for an adhesive to provide firm adhesion between those surfaces and an overlying membrane. In addition, burrs and jagged formations on the edges of bars, which were formed by a punching operation, could abrade or penetrate an overlying membrane. Moreover, the edges of metal bars tended to curl upwardly and/or the bars tended to loop and kink or distort those edges when fasteners were passed downwardly through the bars and membrane to seat in a roof and then overtightened; and those edges could abrade and/or penetrate an overlying membrane. When the bars were made of heavy gauge metal to reduce the curling, kinking, looping and distortion, the cutting of bars from large coils became a problem. Furthermore, the heads of fasteners extended upwardly above the surfaces of the metal bars and resulted in abrasion or penetration of the membranes. Where the batten bars were made from aluminum, the cost was high and the gauge of metal was thick. Where the batten bars were made from galvanized metal the bars were subject to corrosion, particularly where they were drilled or were cut to length in the field. As a result, the use of metal batten bars to secure single ply membranes to roofs has been objectionable.